1. Field of the Invention
The present invention relates to an electrical (or electronic) component with direct transfer on to a printed circuit, in contrast to transfer by plugging-in.
2. Description of the Prior Art
It is increasingly preferable, in the electronic sector, to use surface-mounting components which have many advantages over plug-in components. Mention will be made, as a reminder, of greater miniaturization, higher reliability, a weight saving, an improvement in the signal transit speed, better resistance to vibrations, etc. Furthermore, they afford greater ease of assembly by means of automatic production lines.
This type of component can be passive or active. It can be a capacitive element or a varistor, the latter being used in the sector of protection against electrical overvoltages.
There are two known types of component of this type in "chip" form, according to whether they are protected by a simple protective layer (as in European document No. 229,286) or whether they are embedded in a protective resin, as with the devices according to Japanese documents JP No. 86,219,440 or JP No. 86,235,478.
The devices of the first type have connecting electrodes for the component which are symmetrical in relation to a longitudinal mid-plane of the component. In other words, each of the mutually opposite parallel faces by means of which the ,chip can be connected to the printed circuit each possesses two electrodes. This geometrical arrangement makes it possible to do without an orientating operation to offer the component to the printed circuit, this being advantageous where an automatic feed is concerned. Their main disadvantages are that they have scarcely no resistance in a hot and humid atmosphere because of too great a difference in the coefficients of expansion of the various elements of the component (ceramic, glass, metal) and a fixing-together of these elements by contact and pressing.
Where the devices of the second type are concerned, there is a satisfactory resistance to an aggressive atmosphere, but the electrodes have no symmetry, with the result that the component has to be oriented before it is mounted on the printed circuit.
The present invention is intended to combine the advantages of the two types of component mentioned above by eliminating their disadvantages.